Flat panel devices are well known in the art. Flat panel devices provide numerous benefits, such as compactness and low weight. In certain types of flat panel devices, such as matrix-addressable field emission displays and electroluminescent displays, elements on one of two device panels need to be precisely aligned with the elements on the other device panel. For example, a flat panel field emission display has electron emitters on a cathode plate that must be precisely aligned with phosphors on an anode plate. Typically, an array of electron emitters is aligned with an array of phosphor deposits.
To achieve proper alignment between the opposing plates of the final product, the opposing plates of the device are first brought into alignment, such as by optical methods. Then, the initial alignment must be maintained during subsequent fabrication steps. For a field emission display, the initial alignment step is typically followed by handling steps and heat treatments, such as are required to form hermetic seals between the opposing plates. During these processing steps, the alignment must be maintained to within predetermined tolerances. As the resolution of a display is increased, the alignment tolerances require smaller relative displacements of the aligned elements. Thus, high-resolution devices require very precise alignment methods.
It is known in the art to use fixtures to maintain alignment. These fixtures are typically clamped to the opposing plates after the initial alignment step. The clamped fixtures maintain the relative positions of the opposing plates during the subsequent handling and heating steps. However, prior art clamping fixtures are known to cause misalignments outside desired tolerance levels.
It is known to use alignment fixtures made of stainless steel. It is also known in the art to use glass substrates for the opposing plates of a field emission display. Alignment of high-resolution field emission displays has been observed to be poor using prior art stainless steel fixtures. The misalignments are due to the differing expansion rates of the stainless steel and the glass substrates during heat treatments.
During the hermetic sealing process, the opposing plates of the device typically are displaced inwardly toward one another. A disadvantage of the above prior art alignment method is that during this vertical relative displacement, the clamping force exerted by the clamping fixture on the plates can change, causing relative lateral displacement between the plates.
Accordingly, there exists a need for an improved method for fabricating flat panel devices, which provides improved alignment between the opposing plates of the flat panel device.